A number of packages and packaging methods have been proposed over the years for economically and reliably delivering or relaying an "armed" suture i.e., a suture having a surgical needle attached, to a surgeon in a sterile condition. Besides maintaining sterility of the armed suture, its packaging must also provide convenient dispensing of the suture under the demanding conditions of surgery. Some of the systems proposed are the subject of U.S. Pat. No. 4,967,902 to Sobel et al., U.S. Pat. No. 5,052,551 to Cerwin et al, and U.S. Pat. No. 5,887,706 to Pohle et al. Those patents disclose generally oval suture packages, having a central needle park for holding or "parking" the surgical needle and a peripheral channel for receiving the suture filament attached to the needle. The clearance between successive filament loops and the suture channel, the shape of the channel, and the material composition of the package, are said to be designed so that the suture can be withdrawn from the package without binding in the suture channel.
Because of the widespread use of armed sutures, their packaging and production occurs on a large scale, such that small changes in their design and/or production methods can generate large implications in terms of the expense and efficiency of production, as well as energy and material costs.
Particular problems are associated with armed metallic sutures, such as sternotomy closure sutures. These are used to rejoin ("approximate") the sternum following open chest surgery. The procedure in which the sternum is opened, usually by means of a specially designed surgical saw, is known as a median sternotomy. The act of closing the sternum is termed a sternotomy closure. This must be done with very strong and reliable suture material.
The procedure typically involves the passing of the needle attached to the stainless steel suture through the solid bony structure of each side of the separated parts of the sternum, tightening the joined sternum structure, and ultimately twisting the suture so that the joined sternum will not move during the healing process. In some instances, the suture is passed around one or both parts of the separated sternum and then tightened by twisting the wire suture.
After the suture is adequately tightened, the ends of the suture are cut off, and the portion of the twisted suture bearing the cut ends is bent to be in contact with the joined sternum, so that the cut ends do not injure other tissues. The sutures are left in the patient, and continue to provide support, even after the portions of the sternum have grown back together and healed.
The procedure typically involves the application of a number of sutures along the length of the sternum.
Stainless steel sutures are the sutures of choice for such applications. Stainless steel sutures have extremely high tensile strength relative to its diameter. It is a monofilament suture material which is inert in tissue. When implanted in areas of infection, stainless steel sutures will not split spontaneously, nor necessitate removal in order for wound healing to occur.
The application of the sutures involves stressful twisting, lifting and tightening of the suture material in order to provide a secure closure of the patient's chest. For adequate healing of the sternum, the sutures must hold the portions of the sternum together throughout the healing process. Coughing and other patient movements can put tremendous stress on the sternum, and thus on the sutures during the healing process. If the sutures are not tightened sufficiently to hold the bone portions together tightly during such stressful conditions, proper healing may not take place, resulting in unnecessary pain for the patient, and sometimes necessitating reopening the wound, re-breaking of the sternum, and setting new sutures to support the healing process.
For that reason, the sutures are preferably twisted to very high tightness. Often they are twisted to the point where the surface patina of the suture material changes, indicating a close approach to the maximum tensile strength of the material.
The required manipulations of sternotomy sutures necessitate that the length of the sutures used must be far in excess of the length of the suture material left in the patient. Surgeons commonly require sternotomy sutures greater than twelve inches long for use with adults.
Until now, sternotomy sutures have been sterilely packaged in long cardboard envelopes, typically 19 to 22 inches in length. Those envelopes are overwrapped with a chevron sleeve made of plastic films joined in a manner which maintains sterility within the sleeve, but permits separation of the films to permit access to the sterile cardboard straight pack in the sterile filed of the operating room. Each straight pack contains the number of sutures needed for the operation, with the needle ends of the sutures placed at the opening end of the envelope.
The size of these stainless steel sutures, and the manner of their packaging have caused problems in the past. Normally, prior to surgery, a surgical nurse has to go in and pull all sutures needed for the case, and work them on to the sterile field, ready to go into the surgeon's hand. Typically open the covering flap, tear off the top, and place the opened package on a sterile Mayo stand, along with all of the other sterile products to be used during the operation.
During surgery, the sutures must be provided, one at a time, on demand. The sutures are pulled from the straight pack and placed in a needle holder, for application to the sternum. Working with surgical gloves, it is easy to grab more than on suture or needle. Extraction of the suture from the straight pack may cause one or more other sutures to accompany it out of the pack. If a suture falls out of the sterile field, it must be re-sterilized or replaced. Wire sutures are also more difficult to handle than other suture materials, since both the needle end and the tail end of the suture have the capability to pierce surgical gloves, which also wreaks havoc on the sterile field. Time is often crucial in open chest surgery, so each delaying or disrupting factor can have substantial influence on the outcome.
Wire sutures also have a tendency to kink or undergo plastic deformation, which forms weak points in the suture, leading in some cases to broken stainless steel wires inside patients, which necessitates reopening of the wound and correction of the problem.